Monitoring and Diagnosis of Electrical Equipment Insulation with the Support of Combined Conventional and Alternative Partial Discharge Methods

In this paper, the simultaneous use of conventional and alternative PD methods on high-voltage electrical equipment is described. The sensitivity of each method to detect critical insulation defects is directly compared. The advantage of synchronized PD measurements and the visualization of the measurement data coming from different types of PD sensors gathering signals in different frequency ranges on power transformers, such as coupling capacitors, high-frequency current transformers, transient earth voltage or acoustic sensors, is shown. The synchronous multi-channel PD evaluation technique is successfully used to evaluate the PD data. Many insulation defects develop over the lifetime of electrical equipment and PD monitoring is proposed to detect such changes at an early stage. The advantages of having PD monitoring systems working together on a 500 MVA power transformer and a 220 kV XLPE cable line are shown.